Diet Beverages and Body Weight

Overweight and obese adults who drink diet beverages consume significantly more solid-food calories—particularly from snacks—than those who drink sugary beverages. The findings highlight the challenges in using diet beverages to help control weight.

Excess weight can raise your risk for type 2 and gestational diabetes, heart disease, cancer, and other health problems. But maintaining a healthy weight is difficult for many people. Body weight reflects a complicated balance between the amount of calories consumed and the amount of energy used by the body.

Diet beverage use has skyrocketed in recent decades. It's now a common weight control strategy. It might make sense to think that diet beverages would help you lose weight due to their lack of calories. But the body's mechanisms for maintaining weight are subtle and complex. Studies into how diet beverages affect weight control have found conflicting results.

To gain a better understanding of the relationship between diet beverage consumption and caloric intake, a research team led by Dr. Sara N. Bleich at the Johns Hopkins Bloomberg School of Public Health examined patterns of food and beverage consumption. They used data collected between 1999 and 2010 in the National Health and Nutrition Examination Survey (NHANES), a periodic survey of the health and habits of the U.S. population by the Centers for Disease Control and Prevention. The analysis was funded by NIH's National Heart, Lung, and Blood Institute (NHLBI).

The researchers studied almost 24,000 adults, age 20 and older, who reported all the food and beverages they had consumed in a previous 24-hour period. Results appeared online in the American Journal of Public Health on January 16, 2014.

The team found that 11% of healthy-weight, 19% of overweight, and 22% of obese adults drank diet beverages. Diet drinks appeared to help healthy-weight adults maintain their weight. These adults consumed less food and significantly fewer total calories on a typical day than did healthy-weight adults who drank sugared drinks.

The total calories consumed by overweight and obese adults who drank diet beverages, however, were similar to that of those who drank sugary beverages. Heavier adults who drank diet beverages tended to eat more calories in the form of solid food. Overweight and obese adults who drank diet beverages consumed 88 and 194 more calories from solid foods per day, respectively, than those who drank sugared beverages.

To understand these differences in solid-food intake, the scientists took a closer look at patterns of solid-food consumption. Notably, obese adults who consumed diet drinks ate significantly more snacks than those who had sugared drinks. Those who drank diet beverages consumed 131 calories per day in salty snacks and 243 in sweet snacks, compared to 107 and 213, respectively, for obese adults who drank sugared drinks.

"The results of our study suggest that overweight and obese adults looking to lose or maintain their weight—who have already made the switch from sugary to diet beverages—may need to look carefully at other components of their solid-food diet, particularly sweet snacks, to potentially identify areas for modification," Bleich says.

Controlled studies would be needed to confirm these results. Nevertheless, the research highlights the need for heavier adults who drink diet beverages to closely monitor their food intake.